Technically, WIM can be implemented in several ways. The main differences are in business and everyday usage considerations. The first implementation models in the current phone types will be SIM/WIM solutions, where the security module is stored on the operator-issued Subscriber Identity Module (SIM) card. However, the mobile network subscription functionality is separated from the other applications that require authentication and signature capabilities. Standardised features and interfaces are used to ensure interoperability between the technologies of different manufacturers and the SIM cards of different operators.
In the future, one implementation model for security modules can also be a Dual Chip approach. This means that a second separate SIM-sized smart card containing the security module is placed semi-permanently in the phone. It is removable and issued independently of the SIM card, e.g. by a mobile commerce service provider. Its strength is that it separates the network subscription from the other applications, thus creating more latitude in terms of business models. Naturally, this requires phone designs that have the possibility of storing two SIM-sized cards.